This study will define specific components of cerebral activity preceding movement of the digits in man. At present, there is minimal information in man regarding how the motor cortex provides an appropriate output to the peripheral musculature involved with the fine coordinated use of the digits. The specific aims of this study are to define how cerebral activity (motor potential) in man is correlated with specific movement tasks involving the thumb and forefinger. Movement variables such as load opposing movement, expectancy of load, displacement and velocity of movement will systematically be examined while recording the cerebral activity associated with that particular movement. Analysis will be performed across 28 different movement conditions which will result in the accumulation of a data matrix consisting of 84 movement variables for a particular digit-task. Three different tasks will be examined involving thumb flexion, forefinger flexion and a task involving combined thumb and forefinger flexion. Electromyogram activity will be recorded from a specific flexor muscle involved with the appropriate digit to determine onset time of muscle activation and duration of electromyogram activity associated with a particular movement task. The characterization of specific temporally defined components of the motor potential and their correlation with movement variables will represent a major advance in the present state of knowledge. An evaluation of how the cerebral cortex outputs information required for movement of the digits also represents a new concentration of study in the area of motor control which has predominantly concentrated on more proximal movements. Long term objectives will involve an evaluation of significant movement variables with different age groups ranging from the present subjects (20-35 years) compared with older age groups (36-50 years and 51-65 years). Also, once a normative data base is established patients with cerebral hemisphere strokes will be evaluated at several times in their recovery to examine whether there may be a pronostic indication which may suggest or parallal their clinical recovery in terms of their ability to utilize the digits in a dextrous manner.